I have an excel sheet that works for 90% of people, however some are getting
a vb error "Compile Error" "Can't find project or library"

I can't reproduce the error but I have seen it happen. It always points to
this bit of vb and they don't have to click on this cell it can be any cell.

For me it can't be the vb itself since everyone would get it, so I'm
assuming it's a setting thing. I have checked that they are using the same
date / language as me and macros are enabled so I am at a loss.

This is the vb code

Private Sub Worksheet_SelectionChange(ByVal Target As Range)
If Target.Address = "$I$30" Then 'Change this
Calendar1.Visible = True
Calendar1.Value = Date
Else
Calendar1.Visible = False
End If
End Sub